Multiphase thermoplastic resin compositions

ABSTRACT

The invention relates to a thermoplastic composition comprising at least one polymer (M) forming a matrix in which are dispersed nodules of at least one polymer (K) which are encapsulated in at least one polymer (S) in such a way that these encapsulated nodules are smaller than the nodules of the polymer (S) which are dispersed in the matrix (M).

The invention relates to multiphase thermoplastic resin compositions andmore particularly to compositions in the form of a matrix in whichencapsulated nodules are dispersed.

Many thermoplastics have to be modified by incorporating rubbers orother polymers, for example in order to modify the flexural modulusthereof or to improve the impact strength.

The Applicant has discovered that encapsulated nodules could be smallerthan nodules formed only from the polymer of the capsule.

This has many advantages, for example when the polymer of the matrix istransparent or even translucent, the reduction in the size of thenodules increases the transparency or makes the polymer more translucentfor a constant level of dispersed phase.

U.S. Pat. No. 5,070,145 describes compositions consisting of 80 parts ofnylon-6 (PA-6) or nylon-6,6 (PA-6,6) in which 20 parts of a mixture (i)of a copolymer of ethylene and of an ethyl or butyl acrylate and (ii) ofa copolymer of ethylene, ethyl acrylate and maleic anhydride have beendispersed. These compositions have good impact strength.

EP 284,379 describes multiphase compositions consisting of a polyamideand of an ethylene copolymer in the form of a polyamide matrix in whichnodules (1) of an ethylene-ethyl acrylate-maleic anhydride copolymer aredispersed, and dispersed in these nodules (1) are nodules of polyamides.These nodules (1) are firstly prepared by dispersing a polyamide in theethylene copolymer, and then these nodules are crosslinked and thendispersed in a polyamide. These compositions are also presented ashaving a good impact strength.

Patent FR 2,719,849 describes thermoplastic compositions consisting of amatrix of a thermoplastic polymer in which nodules of a secondthermoplastic polymer, partially or totally encapsulated by an ethylenecopolymer, are dispersed. These compositions are prepared by firstlyencapsulating the second polymer and then the other polymer forming thematrix is added under conditions such that the capsules are notdestroyed. This preparation is carried out in two steps which arecompletely separate or with one step following the other in the sameextruder. These compositions have both good flexibility and good impactstrength. The examples show PA-6, PA-12 or PBT (polybutyleneterephthalate) matrices in which are dispersed nodules of PA-6,6encapsulated by an ethylene-ethyl acrylate-glycidyl methacrylatecopolymer. A comparative example shows that in a PA-6 matrix the PA-6,6nodules encapsulated by the ethylene copolymer are coarser than thenodules formed only from the ethylene copolymer.

The present invention is therefore a thermoplastic compositioncomprising at least one polymer (M) forming a matrix in which aredispersed nodules of at least one polymer (K) which are encapsulated inat least one polymer (S) in such a way that these encapsulated nodulesare smaller than the nodules of the polymer (S) which are dispersed inthe matrix (M).

The polymer (M) may be a mixture of several miscible polymers forming ahomogeneous phase. The same applies to the polymer (K) and the polymer(S). The compositions of the invention may also comprise several typesof encapsulated nodules, for example nodules of (K1) which areencapsulated in (S) and nodules of (K2) which are encapsulated in (S) orelse nodules of (K1) which are encapsulated in (S1) and nodules of (K2)which are encapsulated in (S2).

According to one particular embodiment, the present invention is athermoplastic composition comprising at least one polymer (M) forming amatrix in which are dispersed nodules of at least one polymer (K) whichare encapsulated in at least one polymer (S) such that (i) theseencapsulated nodules are smaller than the nodules of the polymer (S)which are dispersed in the matrix (M) and such that (ii) the proportionof (M) in the (M)+(S) mixtures is essentially the same as the proportionof (M) in the (M)+(S)+(K) mixtures.

Thus, for example, it has been discovered that the nodules of anethylene/alkyl acrylate/maleic anhydride copolymer in a nylon-11 (PA-11)matrix have a size of 0.2 μm while, in the same matrix, the nodules ofnylon-12 (PA-12) which are encapsulated in the same ethylene/alkylacrylate/maleic anhydride copolymer have a size of 0.07 μm (this is thesize Dv (volume diameter) of the nodule together with the capsule, i.e.approximately the external diameter of the capsule).

The compositions of the invention have many advantages:

they are more stable, the morphology of the dispersed phase being finer,that is to say that (M) and (S) have been made more compatible;

they are essentially as flexible as the compositions of (M) comprisingnodules containing only (S) since the polymer (K) may be screened with asufficient thickness of capsule (S). We will return to this point laterin the text;

the finer morphologies also increase the strength of reweld lines;

they are very easy to manufacture, simply by mixing (M), (K) and (S),for example in a short or barely plasticating extruder (standard orbottom-of-the-range extruder) or even directly in an injection press,while in the prior art it is necessary to make them in 2 steps;

they have good flexibility without losing mechanical properties; thus,compositions consisting of (M), (S) and (K) having the same flexuralmodulus as compositions consisting of (M) and (S) have a superiortensile strength. This superior strength may also be manifested by thehigher burst pressure of a pipe manufactured by extrusion of thecompositions of the invention;

they have good impact strength;

(M) need only be, relatively, the major phase in order for it to be thematrix and to avoid phase inversion. For example, it would therefore bepossible to have 35 parts of (M), 32.5 parts of (S) and 32.5 parts of(K); and

in addition to these compositions being particularly stable, they may beprepared and sold in the form of granules and used in conventionalmachines, and may also be recycled, for example if there ismanufacturing scrap due to cutting operations.

The invention relates to the reduction in the size of the nodules of(S), whatever their initial size, when (K) is added.

The polymers (M) and (K) may be chosen from thermoplastics. (M) and (S)are chosen to be compatible. Since (S) is dispersed in the matrix of (M)in the form of nodules, (M) and (S) are deemed to be all the morecompatible the smaller the nodules of (S) are. However, it is estimatedthat if the nodules of (S) are greater than 10 μm they are only slightlycompatible, if the nodules are between 0.5 and 10 μm and preferablybetween 0.5 and 2 μm they are compatible, and below 0.5 μm they are verycompatible.

(K) must be compatible with (S); (K) is therefore selected by preparingdispersions of (K) in (S) and by measuring the size of the nodules. Thisis the general selection criterion and, from the various polymers (K)meeting this criterion another selection is made depending on thedesired properties for the compositions of the invention. This otherselection may depend on the modulus, chemical properties, viscosity,melting temperature and reactivity.

As above, if the nodules of (K) in (S) are greater than 10 μm they areonly slightly compatible, if the nodules are between 0.5 and 10 μm andpreferably between 0.5 and 2 μm they are compatible, and below 0.5 μmthey are very compatible.

It is said that the compatibility of (K) with (S) is the same as thecompatibility of (S) with (M) when the nodules of (S) in (M) have thesame size as the nodules of (K) in (S). It is not necessary for thecompatibility of (K) with (S) to be superior to the compatibility of (S)with (M). Advantageously, the size of the nodules of (K) in (S) must notbe greater than twice the size of the nodules of (S) in (M) and ispreferably approximately the same or smaller. This value of twice, andlikewise the expression "approximately the same", is to be adapted tothe size of the nodules, the measurement accuracy being in fact higherfor the nodules greater than 1 or 5 μm than for the smaller nodules.

It would not be outside the scope of the invention to carry out the testof compatibility of (K) with (S) by measuring nodules of (S) in (K) andthen by proceeding as described above.

(K) must also not be too compatible with (M) in order for them to demixand for (K) to go into the capsule (S). If, then, (K) is strictlyidentical to (M), there will be nodules of (S) in (M). But (K) and (M)may, for example, be two different polyamides or two polyamides derivedfrom the same monomers and having different physical properties. Themeasurements of the compatibility of (M) with (S) and of (K) with (S)are therefore carried out as indicated previously and it is checkedwhether (K) is encapsulated in (S) when (M), (K) and (S) are mixedtogether. Advantageously, (M) and (K) are selected from the same familyof polymers, for example polyamides, saturated polyesters and otherpolymers, as will be described later. Thus, (M) and (K) may be twopolyamides, two polyesters, etc.

It is also necessary to check the reduction in size of the nodules.

The mixing of (M), (K) and (S) is advantageously carried out byintroducing (M), (K) and (S) simultaneously in a device for mixing (K)into the mixture of (M) and (S), or for mixing (M) into the mixture of(K) and (S) or for (S) into the mixture of (K) and (M). However, itwould not be outside the scope of the invention to use various steps ordifferent orders of addition, provided that the desired morphology isobtained.

In addition to the compatibility or incompatibility conditions, the meltflow index (MFI) of (M) is advantageously greater than that of (K).

By way of polymers (M), mention may be made of polyolefins, polyamides,fluoropolymers, saturated polyesters, polycarbonate, styrene resins,PMMA, thermoplastic polyurethanes (TPU), copolymers having polyamideblocks, copolymers having polyester blocks and polyether blocks, PVC,ethylene-vinyl alcohol copolymers (EVOH) and polyketones.

Polyamide (A) is understood to mean condensation products:

of one or more amino acids, such as aminocaproic, 7-aminoheptanoic,11-aminoundecanoic and 12-aminododecanoic acids, and of one or morelactams, such as caprolactam, oenantholactam and lauryllactam;

of one or more salts or mixtures of diamines, such ashexamethylenediamine, dodecamethylene-diamine, m-xylylenediamine,bis(p-aminocyclohexyl)-methane and trimethylhexamethylenediamine withdiacids such as isophthalic, terephthalic, adipic, azelaic, suberic,sebacic and dodecanedicarboxylic acids;

or of mixtures of some of these monomers, which results in copolyamides,for example PA-6/12 by the condensation of caprolactam and oflauryllactam.

Polymers having polyamide blocks and polyether blocks result from thecopolycondensation of polyamide blocks having reactive ends withpolyether blocks having reactive ends, such as, inter alia:

1) Polyamide blocks having diamine chain ends with polyoxyalkyleneblocks having dicarboxylic chain ends;

2) polyamide blocks having dicarboxylic chain ends with polyoxyalkyleneblocks having diamine chain ends, obtained by cyanoethylation andhydrogenation of aliphatic dihydroxylated alpha-omega polyoxyalkyleneblocks called polyetherdiols;

3) polyamide blocks having dicarboxylic chain ends with polyetherdiols,the products obtained being, in this particular case,polyetheresteramides.

Polyamide blocks having dicarboxylic chain ends derive, for example,from the condensation of aminocarboxylic alpha-omega acids from lactamsor of carboxylic diacids and diamines in the presence of achain-limiting carboxylic diacid. Advantageously, the polyamide blocksare of nylon-12.

The number-average molar mass of the polyamide blocks is between 300 and15,000 and preferably between 600 and 5000. The mass of the polyetherblocks is between 100 and 6000 and preferably between 200 and 3000.

Polymers having polyamide blocks and polyether blocks may also includerandomly distributed units. These polymers may be prepared by thesimultaneous reaction of the polyether and polyamide-block precursors.

For example, it is possible to react polyetherdiol, a lactam (or analpha-omega amino acid) and a chain-limiting diacid in the presence of asmall amount of water. A polymer is obtained having essentiallypolyether blocks and polyamide blocks of very variable length, but alsothe various reactants, having reacted in a random fashion, aredistributed randomly along the polymer chain.

These polyamide-block polyether-block polymers, whether they derive fromthe copolycondensation of polyamide and polyether blocks preparedbeforehand or from a one-step reaction, have, for example, Shore Dhardnesses which may be between 20 and 75 and advantageously between 30and 70 and an intrinsic viscosity of between 0.8 and 2.5 measured inm-cresol at 25° C.

Whether the polyether blocks derive from polyethylene glycol, frompolyoxypropylene glycol or from polyoxytetramethylene glycol, they areeither used as such and copolycondensed with polyamide blocks havingcarboxylic ends or they are aminated in order to be transformed intodiamine polyethers and condensed with polyamide blocks having carboxylicends. They may also be mixed with polyamide precursors and a chainlimiter in order to make polyamide-block polyether-block polymers havingrandomly distributed units.

Polymers having polyamide and polyether blocks are described in U.S.Pat. Nos. 4,331,786, 4,115,475, 4,195,015, 4,839,441, 4,864,014,4,230,838 and 4,332,920.

The polyether may, for example, be a polyethylene glycol (PEG), apolypropylene glycol (PPG) or a polytetramethylene glycol (PTMG). Thelatter is also called polytetrahydrofuran (PTHF).

Whether the polyether blocks are introduced into the chain of thepolyamide-block polyether-block polymer in the form of diols or ofdiamines, they are called, for simplification, PEG blocks or PPG blocksor PTMG blocks.

It would not be outside the scope of the invention if the polyetherblocks contained different units, such as units derived from ethyleneglycol, from propylene glycol or from tetramethylene glycol.

Advantageously, the polyamide-block polyether-block polymer is such thatthe polyamide is the major constituent by weight, that is to say thatthe amount of polyamide which is in the form of blocks and that which ispossibly distributed randomly in the chain represents 50% by weight ormore of the polyamide-block polyether-block polymer. Advantageously, theamount of polyamide and the amount of polyether are in the(polyamide/polyether) ratio of from 50/50 to 80/20.

Preferably, the polyamide blocks and the polyether blocks of the samepolymer (B) have respectively masses Mn of 1000/1000, 1300/650,2000/1000, 2600/650 and 4000/1000.

The term polyolefin is understood to mean a polymer containing olefinunits such as, for example, ethylene, propylene or 1-butene units or anyother alpha-olefin. By way of example, mention may be made of:

polyethylenes such as LDPE, HDPE, LLDPE or VLDPE, polypropylene,ethylene/propylene copolymers or metallocene PEs;

copolymers of ethylene with at least one product selected from the saltsor esters of unsaturated carboxylic acids, or the vinyl esters ofsaturated carboxylic acids.

Advantageously, the polyolefin is selected from LLDPE, VLDPE,polypropylene, ethylene/vinyl acetate copolymers or ethylene/alkyl(meth)acrylate copolymers. Advantageously, the density may be between0.86 and 0.965 and the melt flow index (MFI) may be between 0.3 and 40.

By way of examples of fluorinated polymers, mention may be made ofpolyvinylidene fluoride (PVDF), copolymers containing vinylidenefluoride (VF2), ethylene-tetrafluoroethylene copolymers,poly(tri-fluoroethylene), trifluoroethylene copolymers, homopolymers andcopolymers of hexafluoropropene and homopolymers and copolymers ofchlorotrifluoroethylene. Advantageously, PVDF is used.

By EVOH is meant ethylene-vinyl alcohol copolymers. They derive from thehydrolysis of ethylene/vinyl acetate copolymers, this hydrolysispossibly being incomplete and vinyl acetate units possibly remaining.

By way of example of polyesters, mention may be made of PET(polyethylene terephthalate), PBT (polybutylene terephthalate) or PEN(polyethylene naphthenate).

Polyester-block polyether-block copolymers are copolymers havingpolyether units derived from polyetherdiols, such as polyethylene glycol(PEG), polypropylene glycol (PPG) or polytetramethylene glycol (PTMG),carboxylic diacid units such as terephthalic acid and glycol units(ethanediol) or 1,4-butanediol. The linking of the polyethers and of thediacids forms the flexible segments while the linking of the glycol orof the butanediol with the diacids forms the rigid segments of thecopolyetherester.

Such copolyetheresters are described in Patents EP 402,883 and EP405,227, the contents of which are incorporated in the presentapplication.

By way of thermoplastic polyurethanes, mention may be made of polyetherurethanes, for example those containing diisocyanate units, unitsderived from polyetherdiols and units derived from ethanediol or from1,4-butanediol.

Mention may also be made of polyester urethanes, for example thosecontaining diisocyanate units, units derived from amorphouspolyesterdiols and units derived from ethanediol or from 1,4-butanediol.

Polyketones are polymers containing substantially one mole of carbonmonoxide for each mole of unsaturated monomer. This monomer may beselected from alpha-olefins having from 2 to 12 carbon atoms or theirsubstitution derivatives. It may also be selected from styrene or itsderivatives obtained by substitution with alkyls, such asmethylstyrenes, ethylstyrene and isopropylstyrene.

Preferably, the polyketones are ethylene-carbon monoxide copolymers orethylene-polypropylene-carbon monoxide copolymers.

When the polyketones are copolymers of ethylene, a second monomer andcarbon monoxide, there are at least two ethylene units for one unit ofthe second monomer, and preferably from 10 to 100.

The polyketones may be represented by the formula: --(--CO--CH₂ --CH₂--)_(x) --(--CO-A-)_(y) -- in which A denotes an unsaturated monomerhaving at least three carbon atoms, the x/y ratio being at least 2.

The units --(--CO--CH₂ --CH₂ --) and --(--CO-A-)-- are randomlydistributed in the polyketone chain.

The number-average molar masses may be between 1000 and 200,000,advantageously between 20,000 and 90,000, measured by gel permeationchromatography). The melting temperatures may be between 175 and 300°C., usually between 200 and 270° C.

Syntheses of these polyketones are described in U.S. Pat. Nos.4,843,144, 4,880,903 and 3,694,412, the contents of which areincorporated in the present application.

By way of examples of polymers (K), mention may be made of the sameexamples as the polymers (M).

The polymer (S) is any product which encapsulates (K) in a matrix (M)and such that the nodules thus encapsulated are smaller than the nodulesof (S) in (M). In the sense of the present invention, (S) is any productwhich is in the form of nodules in a matrix (M) and which is also in theform of nodules in a matrix (K) or which may be a matrix containingnodules (K). Advantageously, (S) is a thermoplastic having affinitieswith (M) and with (K) and/or able to react with (M) and (K) or havingaffinities with (M) and able to react with (K), or vice versa.

For example, (S) may be a polyolefin chain having polyamide graftedspecies or polyamide oligomers; thus (S) has affinities with polyolefinsand polyamides.

(S) may also be an ethylene copolymer having maleic anhydride units;thus (S) has affinities with polyethylenes and may react withpolyamides.

By way of example of (S), mention may be made of functionalizedpolyolefins, grafted aliphatic polyesters, polyether-blockpolyamide-block polymers, optionally grafted, and copolymers of ethyleneand an alkyl (meth)acrylate and/or a vinyl ester of a saturatedcarboxylic acid.

(S) may also be a block copolymer having at least one block compatiblewith (M) and at least one block compatible with (K).

The functionalized polyolefin is a polymer containing alpha-olefin unitsand epoxy units or carboxylic acid units or carboxylic-acid anhydrideunits.

By way of example, mention may be made of the polyolefins mentioned withregard to the polymers (M), or SBS, SIS, SEBS or EPDM block polymersgrafted by unsaturated epoxys, such as glycidyl (meth)acrylate or bycarboxylic acids, such as (meth) acrylic acid, or by unsaturatedcarboxylic acid anhydrides, such as maleic anhydride.

Mention may also be made of:

copolymers of ethylene, of an unsaturated epoxy and, optionally, of anunsaturated carboxylic acid ester or salt or of a vinyl ester of asaturated carboxylic acid. These are, for example, ethylene/vinylacetate/glycidyl (meth)acrylate copolymers or ethylene/alkyl(meth)acrylate/glycidyl (meth)acrylate copolymers;

copolymers of ethylene, of an unsaturated carboxylic acid anhydrideand/or of an unsaturated carboxylic acid, possibly partly neutralized bya metal (Zn) or an alkali metal (Li), and optionally of an unsaturatedcarboxylic acid ester or of a vinyl ester of a saturated carboxylicacid. These are, for example, ethylene/vinyl acetate/maleic anhydridecopolymers or ethylene/alkyl (meth)acrylate/maleic anhydride copolymersor ethylene/Zn or Li (meth)acrylate/maleic anhydride copolymers; and

polyethylene, polypropylene, ethylene-propylene copolymers which aregrafted or copolymerized with an unsaturated carboxylic acid anhydrideand then condensed with a mono-aminated polyamide (or a polyamideoligomer. These products are described in EP 342,066.

Advantageously, the functionalized polyolefin is selected fromethylene/alkyl (meth)acrylate/maleic anhydride copolymers,ethylene/vinyl acetate/maleic anhydride copolymers, ethylene-propylenecopolymers which contain mostly propylene, these being grafted by maleicanhydride and then condensed with monoaminated nylon-6 or monoaminatedoligomers of caprolactam.

Preferably, this is an ethylene/alkyl (meth)acrylate/maleic anhydridecopolymer containing up to 40% by weight of alkyl (meth)acrylate and upto 10% by weight of maleic anhydride. The alkyl (meth)acrylate may beselected from methyl acrylate, ethyl acrylate, n-butyl acrylate,isobutyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, methylmethacrylate and ethyl methacrylate.

By way of grafted aliphatic polyesters, mention may be made ofpolycaprolactone grafted by maleic anhydride, glycidyl methacrylate,vinyl esters or styrene. These products are described in Application EP711,791, the contents of which are incorporated in the presentapplication.

The polyamide-block polyether-block polymers were described earlier withregard to the polymers (M). These products may be grafted by vinylchloride or alkyl acrylates. These products are described in Patent EP365,398, the contents of which are incorporated in the presentapplication.

The polymers (M), (K) and (S) may contain plasticizers, fillers, fireretardants, glass fibres, etc.

The Applicant has also discovered that the ratio between the amounts of(S) and the amounts of (K) is important. For theoretical values, i.e.assuming that all the (K) is encapsulated, of the thickness of thecapsule, i.e. of (S), lying between 10 and 30% of the diameter of theencapsulated nodule, i.e. of the (S)+(K) assembly, the compositions ofthe invention benefit most from the combined presence of (S) and (K).

For values which are higher, and advantageously higher than 40%, thereis "screening", the encapsulated nodule producing the effects of anodule of the same size consisting only of (S), i.e. as if (K) werereplaced by (S). The advantage of the invention is nevertheless to havereduced the size of the nodules. For example, if the polymers (M) mustcontain nodules of (S) in order to obtain such or such a property butthese nodules are too coarse, then the polymer (K) is added and the sizeof the nodules is reduced. (K) may be any polymer provided that itreduces the size of the nodules. Flexibility and impact properties arethus preserved, but, for example, there is an improvement intransparency if (M) is suitable, this being in addition to the advantageof a 1-step process, already mentioned.

For smaller values of the thickness of the capsule, i.e. down to valueswhich are just sufficient for (M), (K) and (S) to be in accordance withthe invention, i.e. to be such that the nodules of (K) encapsulated by(S) are smaller than the nodules of (S) alone in (M), the properties of(K) are "added" to those of (M). For example, if (M) is PA-6 and (K) isPA-6,6, the temperature of bending under load (HDT) is increased.

For the aforementioned average thicknesses of (S), the compositions ofthe invention benefit from the effects of (S) and of (K).

It is also possible to be in a limiting case in which, at low strain,(S) essentially screens (K) and which, at high strain, (S) starts to nolonger screen (K). (K) then starts to play a (structural) role byproviding additional strength (as long as (K) has been selected forhaving these properties, for example PA-6,6 while (M) is PA-11).

Thus, for example, the flexibility and impact-strength measurementswould be fully improved as (S) (in this case, a highly flexible impactmodifier) fully screens (K). On the other hand, during bursting of apipe (destructive property, and therefore the corollary of highstrains), the nodule will deform in such a way (the thickness decreasingin the direction perpendicular to the strain) that (S) no longercompletely screens (K), and (K) then adds to the strength.

It would not be outside the scope of the invention if the capsules of(S) were not completely around (K), that is to say that theencapsulation were partial, provided that the size of the nodules is inaccordance with the invention.

The invention is particularly useful in the case of thermoplastics (M)such as polyamides and saturated polyesters.

Advantageously, (M) and (K) are selected from the same family ofpolymers and (S) is selected from ethylene/alkyl (meth)acrylate/maleicanhydride copolymers, ethylene/vinyl acetate/maleic anhydridecopolymers, ethylene/alkyl (meth)acrylate/glycidyl (meth)acrylatecopolymers and ethylene/vinyl acetate/glycidyl (meth)acrylatecopolymers.

Preferably, (M) and (K) are chosen to be very similar to each other inthe same family of polymers, for example PA-11 and PA-12.

According to the preferred embodiments of the invention, polymers havingthe following properties or characteristics are respectively chosen for(M), (S) and (K):

rigid/flexible/rigid

high T_(g) /low T_(g) /high T_(g)

T_(g) >0° C./T_(g) <0° C./T_(g) >0° C. (T_(g) denotes the glasstransition temperature)

semi-crystalline/amorphous or pseudo-amorphous/semi-crystalline

crystalline/amorphous or pseudo-amorphous/crystalline

EXAMPLES

The following designations are used:

PA-11: a nylon-11 having a M_(w) of between 45,000 and 55,000 and notcontaining a plasticizer;

PA-11 p.20: a nylon-11 of the PA-11 type containing (7±2)% by weight ofBBSA (butylbenzene sulphonamide) as plasticizer;

PA-11 p.40: a nylon-11 of the PA-11 type containing (12±2)% by weight ofBBSA.

PA-12: a nylon-12 of M_(w) of from 45,000 to 55,000.

L: an ethylene/butyl acrylate/maleic anhydride copolymer having asproportions by weight 79/18/3 and an MFI of 3 to 6, which is a randomcopolymer obtained by high-pressure radical catalysis.

MFI denotes the melt flow index.

LOTRYL: an ethylene/methyl acrylate copolymer having as proportions byweight 84/16 and an MFI of 0.3 at 190° C., 2.16 kg.

PA-12 p.20: a nylon-12 containing (7±2)% by weight of BBSA.

PA-12 p.40: a nylon-12 containing (12±2)% by weight of BBSA.

EPR_(m) denotes a maleicized EPR (ethylene propylene copolymer).

The results are given in the following table (the % are by weight). Thecompositions indicated in the table correspond to a total of 100%, thepercentage of the major component not appearing. For example: PA-11p.20+6% L+6% PA-12 means that there is 88% of PA-11 p.20 in thecomposition.

In Example 20 (PA-11+5% PASA) means a nylon-11 containing 95% of PA-11and 5% of PASA.

PASA denotes a semi-aromatic polyamide obtained by the condensation oflauryllactam, BMACM [bis-(3-methyl-4-aminocyclohexyl)methane],isophthalic acid and terephthalic acid, as described in EP 550,308.

In the table, the "expected flexural modulus" denotes the flexuralmodulus calculated from the percentages of the constituents withouttaking account of any synergy between the constituents or of themorphology. Thus, in Example 5, a value of 600 MPa is expected becausethere is the same amount of PA and because 600 MPa was measured forExample 3 (the difference in modulus of PA-11 and PA-12 has beenneglected).

                                      TABLE 1                                     __________________________________________________________________________                                                          Optical                      Mechanical properties properties                                                                                         Notched                                                                             Transparency                                             Pipe      Tension:                                                                           Charpy                                                                              good if                        burst  stress impact higha                                                    (stress)  at 50% -40° C. Trans-                                      Flexural Ex- at +23° C.  elonga- (new mission good if                                                                          Com-                                                                        modulus pected                                                                NFR Burst tion                                                                standard) (560                                                                nm, low                                                                        Ex. par-  ISO                                                                178 flex 12632                                                                modulus ISO R                                                                 527 ISO 179:93                                                                2 mm) Opacity                                                                  No. ative                                                                    Composition                                                                   MPa mod. MPa                                                                  °100                                                                   MPa kJ/m.sup.3                                                                % %                __________________________________________________________________________    Unplasticized PA-11 family                                                     1 x  PA12              1100                    7     10   35                    2 x PA11 1000      13 33 36                                                   3 x * + 25% L 600     15 23 46                                                4 x * + 50% L 320  18 6  18 15 60                                             5 x " + 25% L + 25% PA12 450 600 31 7  20 27 43                              29 x " + 10% L 860     14 14 52                                             Superflexible (150-200 MPa) plasticized PA-11 family                           6 x  PA11 p40          300      24             6     19   40                    7 x PA11f15 160  14 8 15 2 28 43                                               8' x PA11p40 + 25% L + 5% Lotryl 180  15 8 16.5 7 13 58                      8 x PA11p40 + 30% L 180  15 8 16.5 7 14 57                                    9 x PA11p40 + 15% L + 15% PA12 185 255 20 11 23 9 20 48                    Flexible (300-350 MPa) plasticized PA-11 family                               10 x  PA11p20           420      32             10    25   40                    6 x PA11p40 300  24 8 24.5 6 19 40                                           11 x PA11p20 + 12% L 320  24 8 24.5 8 16 54                                   12 x PA11p20 + 6% L + 6% PA12 340 430 29 9 31 17 21 47                      Various                                                                       13 x  PA12p40           400      25             4                               14 x PA12p40 + 30% L 195     5 10 47                                          15 x PA12p40 + 15% L + 15% PA12 225 325 21 9   17 40                          16 x PA11P20 + 5% EPR + 7% PA12 360  28 8    1 63                              12' x PA11p20 + 5% L + 7% PA12 355 450 29 8   22 47                          17 x PA11p40 + 10% L + 20% PA12 215  22 10  9 20 48                           18 x PA11p40 + 10% L + 20% HDPE 310  22 7  8  9 56                            19 x PA11p20 + 5% L + 7% PA6 380  29 8  8 16 53                               20 x (PA11 + 5% PASA) + 6% L + 6% PA12 1000       21 40                     Unplasticized PA-12 family                                                    28 x  PA12              1100                    6                               25 x PA12 + 15% L 880                                                         26 x PA12 + 30% L 715  27.5 3.8  9.5 mod. mod.                                27 x PA12 + 15% L + 15% PA11 740 860 30.5 4.1  10 good good                 __________________________________________________________________________                                    Manufacture                                         (possible Exudation Morphology                                               Viscosity even on a (loss of Nodule                                           MFI short, low- plasticizer diameter Encapsulation                         Ex. Com-  235° C., 5 kg mixing when hot) D.sub.v (SEM) Is K                                                                   No. parative                                                                 Composition g/10                                                              mn extruder) %                                                                μm encapsulated                                                            ?                     __________________________________________________________________________    Unplasticized PA-11 family                                                     1 x   PA12                                                                      2 x PA11                                                                      3 x " + 25% L    0.2                                                          4 x " + 50% L    0.3                                                          5 x " + 25% L + 25% PA12    0.2 yes                                          29 x " + 10% L    0.2                                                       Superflexible (150-200 MPa) plasticized PA-11 family                           6 x   PA11P40                                                                   7 x PA11f15  yes -31%                                                          8' x PA11p40 + 25% L + 5% Lotryl  no -9% 0.2                                 8 x PA11p40 + 30% L  no -9% 0.2                                               9 x PA11p40 + 15% L + 15% PA12  yes -9% 0.07 yes                           Flexible (300-350 MPa) plasticized PA-11 family                               10 x   PA11p20                                                                   6 x PA11p40  yes -13%                                                        11 x PA11p20 + 12% L   -6% 0.2                                                12 x PA11p20 + 6% L + 6% PA12  yes -6% 0.07 yes                             Various                                                                       13 x   PA12p40           10                                                     14 x PA12p40 + 30% L 0.3 no -9% 0.2                                           15 x PA12p40 + 15% L + 15% PA 3 yes -9% 0.07 yes                              16 x PA11p20 + 5% EPR + 7% PA12   -6% 0.8 no                                   12' x PA11p20 + 5% L + 7% PA12   -6% 0.07                                    17 x PA11p40 + 10% L + 20% PA12  yes -9% 0.07 yes                             18 x PA11p40 + 10% L + 20% HDPE   -9% 0.9 yes                                 19 x PA11p20 + 5% L + 7% PA6   -6% 0.6 yes                                    20 x (PA11 + 5% PASA) + 6% L + 6% PA12    0.07 yes                          Unplasticized PA-22 family                                                    28 x   PA12              30                                                     25 x PA12 + 15% L 9                                                           26 x PA12 + 30% L 4 no  0.25                                                  27 x PA12 + 15% L + 15% PA11 14 yes  0.15                                   __________________________________________________________________________

What is claimed is:
 1. A thermoplastic composition having an improvedtransparency comprising nodules (1) and encapsulated nodules (2)dispersed in a matrix, wherein:the matrix comprises at least one polymerM; the nodules (1) comprise a polymer S; the encapsulated nodules (2)are smaller in diameter than the nodules (1) alone and formed byencapsulating at least one polymer K in nodules (1) of the polymer S,thereby reducing the size of the encapsulated nodules (2).
 2. Thecomposition according to claim 1, wherein the polymer M is selected fromthe group consisting of polyolefins, polyamides, fluropolymers,saturated polyesters, polycarbonate, styrene resins, PMMA, polyurethanes(TPU), copolymers having polyamide blocks, copolymers having polyesterblocks and polyether blocks, PVC, ethylene-vinyl alcohol copolymers, andpolyketones.
 3. The composition according to claim 1, wherein thepolymer K is selected from the same polymers as the polymer M.
 4. Thecomposition according to claim 1, wherein the polymer S is selected fromthe group consisting of functionalized polyolefins, grafted aliphaticpolyesters and polyamide-block polyether-block polymers.
 5. Thecomposition according to claim 1, wherein the polymer M is polyamide-11(PA-11) the polymer S is an ethylene/alkyl (meth)acrylate/maleicanhydride copolymer and the polymer K is polyamide-12 (PA-12).
 6. Thecomposition according to claim 1, wherein the thickness of the polymer Kinside the encapsulated nodules (2) is between 10 and 30% of the totaldiameter of the encapsulated nodules (2).
 7. The composition accordingto claim 2, wherein the polymer K is selected from the same group ofpolymers as the polymer M.
 8. The composition according to claim 2,wherein the polymer S is selected from the group consisting offunctionalized polyolefins, grafted aliphatic polyesters andpolyamide-block polyether-block polymers.
 9. The composition accordingto claim 3, wherein the polymer S is selected from the group consistingof functionalized polyolefins, grafted aliphatic polyesters andpolyamide-block polyether-block polymers.
 10. The composition accordingto claim 7, wherein the polymer S is selected from the group consistingof functionalized polyolefins, grafted aliphatic polyesters andpolyamide-block polyether-block polymers.
 11. The composition accordingto claim 4, wherein the polymer S is grafted.
 12. The compositionaccording to claim 8, wherein the polymer S is grafted.
 13. Thecomposition according to claim 9, wherein the polymer S is grafted. 14.The composition according to claim 10, wherein the polymer S is grafted.15. The composition according to claim 2, wherein the polymer M isPA-11, the polymer S is an ethylene/alkyl (meth)acrylate/maleicanhydride copolymer and the polymer K is PA-12.
 16. The compositionaccording to claim 3, wherein the polymer M is PA-11, the polymer S isan ethylene/alkyl (meth)acrylate/maleic anhydride copolymer and thepolymer K is PA-12.
 17. The composition according to claim 4, whereinthe polymer M is PA-11, the polymer S is an ethylene/alkyl(meth)acrylate/maleic anhydride copolymer and the polymer K is PA-12.18. The composition according to claim 7, wherein the polymer M isPA-11, the polymer S is an ethylene/alkyl (meth)acrylate/maleicanhydride copolymer and the polymer K is PA-12.
 19. A thermoplasticcomposition having an improved transparency comprising nodules (1) andencapsulated nodules (2) dispersed in a matrix, wherein:the matrixcomprises at least one polymer M; the nodules (1) comprise a polymer S;the encapsulated nodules (2) are smaller in diameter than the nodules(1) alone and formed by encapsulating at least one polymer K in thenodules (1) of the polymer S, thereby reducing the size of theencapsulated nodules (2), and the compatibility between the polymers Kand S are equal to or higher than the compatibility between the polymersS and M.
 20. A thermoplastic composition having an improved transparencycomprising at least one polymer (M) forming a matrix in which aredispersed encapsulated nodules, wherein:the encapsulated nodules areformed of at least one polymer (K) encapsulated in nodules of at leastone polymer (S); and become smaller in diameter than that of the nodulesof the polymer (S) alone when adding the polymer (K) into the nodules ofthe polymer (S).